FIELD OF THE INVENTION
This invention relates to a method and apparatus for welding of U tube to a third
leg tube having bend of varying eccentricity to manufacture bifurcate joints for
power boilers. More particularly, the invention relates to an automated welding
system for welding of irregularly shaped bifurcate components.
BACKGROUND OF THE INVENTION
In power plants, bifurcate assembly is used for pressure part components. This is
used in superheater and reheater areas for transferring the steam. The
configuration of this assembly is advantageous to reduce the number of joints to
the headers. Bifurcates are high volume items required in large numbers for
every boiler. The volume goes still higher for the higher capacity boilers. Meeting
the demand by manual welding is quite difficult. This assembly is presently being
manufactured by using manual TIG process for root followed by manual SMAW
process for fill passes. Accordingly, the bifurcate job configuration is complicated
for welding automation.
The present invention provides an apparatus for accommodating irregular
shaped bifurcate components with perfect alignment and automatic welding of
the job with TIG welding for root pass and MAG welding for fill passes as well as
the design of the machine and process parameter.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an automated welding
system for welding of irregularly shaped bifurcate components.
Another object of the invention is to propose an automated welding system for
welding irregularly shaped bifurcate components, which increases the
productivity and quality of the welded joints.
A still another object of the invention is to propose an automated welding system
for welding of irregularly shaped bifurcate components which allows easy job
loading and joint alignment with accuracy to produce superior quality weld joints.
A further object of the invention is to propose an automated welding system for
welding irregularly shaped bifurcate components, which enables welding of
various types of bifurcates in a single system with faster changeover facility.
These and other objects and advantages of the invention will be apparent from
the ensuing description.
SUMMARY OF THE INVENTION
According to the invention an automatic bifurcate welding system is provided
which is enabled to implement a GTAW process for root pass and a GMAW

process for filler passes. A rotating job holding device is interfaced with the
welding machine to enable easy loading and perfect alignment of the weldable
components, and thus enhancing the productivity many fold. The system can be
used for all bifurcates with different eccentricity that are manufactured.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 shows an automated welding system according to the invention.
Fig. 2 indicates head assembly of the system with the U bend held on the head
assembly.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Fig. 1 shows a welding system for the bifurcate automation. The job is mounted
between a front end motor (4) and a rear end motor (8). The U bend is held in
the head assembly of the machine and the third leg is held in a movable rest
heat (6). A weld head assembly is described separately in Fig. 2. On the machine
carriage (1) a TIG torch (2) and MIG torch (3) is mounted each being free to
move in a single direction. The Motor (4) rotates the u bend, and a rear end
drive (7) rotates the third leg. A tag weld is first made by the TIG assembly (2)
and the job is rotated to complete the root welding. After completion of the root
weld, the TIG assembly (2) goes to home position, and the torch (3) MIG comes

forward and completes the weld joint. TIG assembly (2) and MIG assembly (3)
has separate power sources. TIG can be water cooled or air cooled as per
specification.
Fig.2 shows a BIFURCATE HEAD ASSEMBLY of the U bends. This is an assembly
of a plurality of components and allow centering of the U bends with the third
leg. All the components are described hereinbelow:
• Horizontal Adjustment Component - (28) - This provided means for
horizontal adjustment of the job.
• Vertical adjustment—(29) and vertical holding plate (25) - allows
holding the job vertically including making vertical adjustment.
• Clamping nuts, bolts and washers of different sizes (2, 3, 5, 7, 8, 10,
11,12,14)
• U bend (27)
• Locating pin (9)
• Holding screw (10)
• Clamping plate (6)
• Vertical tilting screw (32)
• Side plate (1)
• Horizontal holding plate (31).
The disclosed system can be used for U bends of any diameter including
third legs of corresponding diameters at power plant application.

The system is adaptable to STT or similar process for root pass by using
corresponding power source or similar other power sources. The system
allows multi pass welding in TIG and MIG, and a number of WPS/POR for
different material in both processes, can be used. According to the invention,
welding of bifurcates with or without preheating and post heating can be
done. A variety of TIG electrodes and wire is useable. Different shielding
gases can be used with or without purging. The system caters for welding of
bifurcates of carbon steel and alloy steel.

WE CLAIM:
1. An automated welding system for bifurcate welding, comprising:
a front end motor (4);
a rear end motor (8);
an irregular shaped bifurcate object (27) held in a weld head
assembly for welding to a third leg, the third leg being placed
in a movable clamping plate (6);
a TIG torch assembly (2), and a MIG torch assembly (3)
rotatably mounted on the machine carriage (1), the torch
assemblies (2, 3) being free in a single direction;
the TIG torch assembly (2) is enabled to first move forward to
carry-out the root welding while both the bifurcate (27) and
the third leg is rotated respectively by the front end and rear
end motors (4, 8) and return to home position, the MIG torch
assembly 3 being activated upon return of the TIG torch
assembly (2) to home position and complete the weld joint,
wherein the weld head assembly is configured to have
horizontal and vertical holding plates (25, 31) to hold the
object (27), the clamping plate (6) to hold the third leg, one
each vertical and horizontal adjustment means (29, 28), a side
plate (1), and a plurality of nuts, bolts, washers (2, 3, 5, 7, 8,
10-14), and at least one each holding screw and locating pin
(10, 9).

2. An automated welding system for bifurcate welding of irregularly
shaped bifurcate components substantially as herein described
and illustrated with reference to the accompanying drawings.

This invention relates to an automated welding system for bifurcate
welding, comprising a front end motor (4) a rear end motor (8); an irregular
shaped bifurcate object (27) held in a weld head assembly for welding to a
third leg, the third leg being placed in a movable clamping plate (6); a TIG
torch assembly (2), and a MIG torch assembly(3) rotatably mounted on the
machine carriage (1), the torch assemblies (2, 3) being free in a single
direction; the TIG torch assembly (2) is enabled to first move forward to
carry-out the root welding while both the bifurcate (27) and the third leg is
rotated respectively by the front end and rear end motors (4, 8) and return
to home position, the MIG torch assembly (3) being activated upon return of
the TIG torch assembly (2) to home position and complete the weld joint,
wherein the weld head assembly is configured to have horizontal and vertical
holding plates (25, 31) to hold the object (27), the clamping plate (6) to hold
the third leg, one each vertical and horizontal adjustment means (29, 28), a
side plate (1), and a plurality of nuts, bolts, washers (2, 3, 5, 7, 8, 10-14),
and at least one each holding screw and locating pin (10,9).